Quick Links

Load path from deck 'h-in. by 8 in. galvanized anchor bolt embedded in concrete - / Finished grade PIERS TRANSFER THE DECK'S WEIGHT TO THE SOIL 12-in. builder's tube To do so effectively, they need to be sized and spaced according to the deck's design load and the soil's bearing capacity (sidebar p. cold climates, piers always should sit below the frost line to prevent frost heaves. Check your local code for pier-depth requirements. 46). sit on undisturbed soil below the frost line. Footings spread the weight over a larger area When using a spread footing, the load is distributed over a larger surface area than a builder's tube alone can cover. If the piers will be used in soil with poor bearing capacity or if the deck has a heavy design load, use a spread footing to distribute the load over a greater surface area. The more expensive, labor-intensive way to do this requires a relatively large excavation for each pier. After forming and pouring the footings, you have to install the tubes and backfill around them, then complete a second pour for the piers. But plastic footing forms bring this process down to just one pour. For most of these systems, a builder's tube is fastened to the top of the form; then the assembly is lowered into the hole, backfilled, and poured in one shot. See the manufacturer's Web site for sizing and load requirements. Sq uare Foot www.sqfoot.com Available from 22 in. to 32 in. dia. Cost: $16 to $30 per form 24-in.-wide spread footing BigFoot Systems www.bigfootsystems.com ... Available from 20 in. to 36 in. dia. Cost: $18 to $75 per form The Foot ing Tube EVERYTHING YOU NEED A few tools, even fewer materials, and a little sweat will get most deck foundations out of the ground in less than a day. • • • • www.footingtube. com A builder's tube and spread footing in one. Top diameter sizes range from 6 in. to 12 in. Cost: $33 to $47 per form � Redibase www.redibase-form.com Available in 24 in. dia. Cost: $9 to $12 per form Drawings: Dan Thornton Builder's tubes • • • • • • 80-lb. bags of ready-mix concrete Garden hose Foundation spikes Batterboards . 1J2-in. by 8-in. anchor bolts, nuts, and washers Adjustable post bases Post-hole digger Digging bar Electric concrete mixer Stabila plate level In JUNE/JULY 2006 45